Process and apparatus for removing carbon from still tubes



Dec. 12, 1933.

PROCESS A. JIEULBERG 1,939,112

AND APPARATUS FOR REMOVING CARBON FROM STILL TUBES Filed Sept. 8, v1932 {/l I/l ICIA F] J 51)) r /1|3 1 15 JEaZAer Q.

Patented Dec. 12, 193.;

PROCESS AND APPARATUS FOR REMOVING CARBON FROM STILL TUBES Adam J. Eulberg, Sunburst, Mont.

Application September 8, 1932. Serial No. 632,257

3 Claims.

This invention relates to processes and apparatus for removing carbon from oil cracking still tubes and the like, and has for an object to provide a process in which the combined action of heat for loosening the carbon, steam pressure for carrying it out, and the cutting action of a gravel blast, is used to effectively remove carbon and likedeposits in minimum time without injury to the tubes.

Steam has hitherto been utilized in carbon removal from oil cracking still tubes but with varying success since carbon spots remain in the tubes, which spots seem to be burned too hard for the steam and heat to carry off. I have discovered that by applying gravel to the steam blast that the hammer blows of the irregular hard stones fracture and loosen the burnt spots of carbon so that cracking tubes are restored to practically new condition.

It is also known that steam has been hitherto passed through the hot oil cracking tubes alternately with the passage of oil through the tubes to purge the tubes without interrupting the work but this results in a loss of about one-half the operating time of the still. I have discovered that this loss of time may be saved by heating the carboned tubes to a cherry red and thereupon passing steam at 100 pounds, or greater, pressure through the heated tubes to soften and carry off the major portion of the carbon in a few minutes, whereupon the subsequent gravel blastong step, under the steam pressure, will effectively remove all of the remaining hard burnt carbon spots which the initial steam pressure step failed to eradicate.

For a full understanding of the steps of the process and the apparatus used in carrying out the invention reference may be had to the accompanying drawing in which Figure 1 is a 40 vertical section through a portion of an oil cracking still showing the application thereto of the apparatus used in practicing my carbon removing process. 4

Figure 2 is an enlarged detail section through 5 the gravel and steam connections to the oil cracking tubes, and

Figure 3 is a detail section of the gravel and steam exhaust valve.

Referring now to the drawing in which like which coacts with the front and rear walls of the characters of reference designate similar parts u in the various views, 10 designates a portion of still in supporting the oil cracking tubes 14. As usual the oilinlet 15 is carried by the lowermost tube while the uppermost tube is equipped with an oil outlet pipe 16 which conducts the hot oil to the evaporator or cracking chamber. Heat passing from the combustion chamber over the uppermost coils of the cracking tubes and thence downward over the lowermost coils to the stack produces an accumulation of hard carbon scales in the tubes which in time chokes the tubes and 5 this deposit is found greatest in the uppermost tubes due perhaps to the heat being more directly applied to these tubes as they pass through the combustion chamber, as shown.

To remove the carbon deposits on the oil cracking tubes I attach a steam pipe 17 to the oil inlet and admit steam under approximately 100 pounds pressure. However, a greater pressure is better than a pressure below 100 pounds, in practicing the process. Prior to admission of the steam a fire is built in the combustion'chamber and obviously the heat will raise the temperature of the oil cracking pipes as well as the steam passing therethrough; It is found that when the pipes become cherry red that the effect of the steam g0 blast is most pronounced, at which time the temperature of the steam exhausting through the pipe 16 has been found, in practice, to be sub stantially 1200 F. Preferably, for carrying of]? the exhaust steam into the atmosphere I apply a three-way valve 18 to the exhaust pipe 16, the valve casing being preferably equipped with a discharge nozzle 19, although this may be dispensed with if desired.

Moreover, it is not essential that the exhaust steam be discharged in the atmosphere since the valve 18 may be dispensed with and'the steam, together with the carbon picked up thereby, be allowed to enter the evaporator or cracking chamber. In practice, a few minutes application of the steam blast under the specified pressure and under the specified temperature has been found sufficient to remove practically all of thecarbon deposit in all of the oil cracking tubes.

There will remain, however, in the oil cracking 10o tubes, especially the uppermost coils of the tubes, hard burned spots of carbon which superheated steam under pressure is unable to disintegrate and dislodge. To remove these spots the following apparatus may be employed.

A pipe 20 is coupled to the oil cracking tubes preferably to the lowermost tubes of those uppermost .coils, which pass through the combustion chamber, as shown in Figure 1. A conventional T coupling 21 may be used to effect applino cation of the stand pipe 20 to the oil cracking tube. The stand pipe 20 is equipped at the top with a valve 22 and near the bottom with a valve 23 and at the top may be equipped with a hopper 24. The upper valve is open and the hopper filled with gravel which will contain a. quantity of pebbles, stones and the like. When the stand pipe is filled with this gravel the upper valve may be closed and the lower valve then may be opened to permit the gravel gravitating and merging with the superheated steam blast at the T coupling 21.

The hard pebbles, stones and the like, carried along by the high velocity of the steam blast impinge against and deliver hammer blows upon the residual hard burnt carbon spots. This continuous shower of hammer blows has been found to disintegrate, crack up and dislodge the hot carbon spots so that the steam blast may carry the dislodged particles from the oil cracking tube. The high temperature and high pressure of the steam, of course, coacts with the bombarding of the gravel to soften, disintegrate, pulverize and loosen the carbon spots so that a few minutes application of the gravel and steam blast, or at least sufficient time to permit the contents of the stand pipe 20 to enter the oil cracking tubes, has been found suflicient to thoroughly cleanse the interiors of the tubes and restore practically their original newness and brightness so that the passage of oil therethrough during the cracking process will be substantially equal to that of new tubes.

Although I have shown a stand pipe as the means for supplying gravel to the steam blast it will be evident that various other apparatus may be equally well employed to effect the same process and therefore it is not intended to limit the scope of the invention to the particular apparatus shown and described.

What is claimed is:

1. A process of purging oil cracking tubes of carbon deposits consisting of blowing steam through the tubes from the oil input end to the oil output end while simultaneously heating the tubes to substantially a cherry red, and subsequently admitting a stream of gravel-like ma terial to the steam blast.

2. A process of purging oil cracking tubes of carbon deposits consisting of heating the tubes, admitting steam, raising the temperature of the steam blast to approximately 1200" F. by heating the tubes, and subsequently admitting a stream of gravel-like material to the steam blast while maintaining the pressure and temperature of the blast.

3. In an oil cracking still, means for admitting to and exhausting from the oil cracking pipes of the still a steam blast, a stand pipe operatively connected to the oil cracking tubes at a point between the intake and outlet of the tubes, and a pair of valves carried by the pipe adapted to be alternately opened to permit the pipe being first supplied with a gravel-like material and then to permit the pipe to discharge said material into the path of the steam blast.

ADAM J. EULBERG. 

